This invention relates to a cap for sealing a container having contents from which gas dissociates therein. The invention also relates to a cap which is adapted to provide an opening in the container to gain access to the contents as well as seal the opening thereafter. The invention further relates to a cap in combination with a container end suitable for sealing a container having contents from which gas dissociates therein, and a method of making such can end.
There has been a long-felt need for a snap-type cap which is effective for sealing and/or resealing a container having a gas dissociating substance, such as a carbonated beverage, for example, packaged therein. When a beverage container is opened, gas in the space between the beverage and the container end (referred to as head space) is immediately lost, and gas which subsequently dissociates from the beverage escapes as well. Any gas loss has an effect on the level of carbonation in the beverage and excessive loss may make the beverage unacceptable. A cap suitable for sealing or resealing must be effective in sealing to make the container substantially gas-tight, and it must also remain in sealing engagement at relatively high pressures. Since the level of carbonation from one beverage to another may vary substantially and internal pressure may also vary with other factors, such as temperature and head space above the beverage in the container, for example, it is not practical to establish a performance criteria for a beverage closure which will satisfy every potential use. Typically, however, a cap suitable for providing substantially gas-tight sealing of a beverage container should be able to retain approximately 90% of the level of carbonation in the beverage at the time of sealing for a period of 24 hours at a pressure of up to approximately 50 psi and with the beverage at room temperature. Many attempts to solve the problem of gas-tight sealing against such relatively high pressures with a snap-type cap have been made as evidenced by the number of patents which are directed thereto. A large number of proposals have been made to incorporate a central stopper with the cap, whereby the stopper acts against an interior surface of the bottle neck to effect a seal. Examples of but a few of such patents are Salminen U.S. Pat. No. 3,209,934, Lovell U.S. Pat. No. 3,254,785, Lohrer U.S. Pat. No. 3,266,652, Lohrer U.S. Pat. No. 3,438,529, Sachau U.S. Pat. No. 3,528,091 , Grussen U.S. Pat. No. 3,858,742, Beck U.S. Pat. No. 3,866,784, Aichinger et al U.S. Pat. No. 3,872,993 and Pirgov et al U.S. Pat. No. 3,994,410. A number of other patents describe stopperless caps which rely solely upon the hoop strength of the cap skirt surrounding the bottle mouth to provide a seal between the cap and bottle. Examples are Gelbjerg-Hansen et al U.S. Pat. No. 3,247,993, Fuglsang-Madsen et al U.S. Pat. No. 3,247,994 and Ruprecht U.S. Pat. No. 3,371,814.
There has also been a long-felt need for sealing the opening in a carbonated beverage can. Easy-open ends as closures of carbonated beverage cans have become increasingly popular because their usage eliminates the need for a separate opener. A disadvantage, however, of many of the first embodiments of such closures is that the opening panel is a scored portion of the can end which is torn away and separated from the can by lifting and pulling on an attached tab. Careless discarding of the separated portion by users, particularly in public places, has contributed to an evergrowing litter problem, and a new generation of can ends commonly referred to as ecology ends has come into usage. The ecology ends, in general, feature an opening panel which is only partially severed from the end to provide an opening, and thus the panel remains attached to the can end. An example of such a can end is described in Heffner U.S. Pat. No. 3,618,815 wherein a V-shaped panel in the can end is forced into the can by an opening tab which is attached to the can end, and the panel remains attached along the hinge line.
An ever-increasing share of the 12-oz. carbonated beverage market is being packaged in cans rather than bottles for such reasons as more efficient use of shelf, storage and shipping space per ounce of beverage packaged, savings in container cost, and savings in cost in packaging the beverage in the container. In addition, cans are lighter and are less susceptible to breakage than glass bottles and provide a package having a longer shelf life than does a plastic bottle. Furthermore, it is readily apparent to any purchaser of carbonated beverages, whether beer or soft drinks, that practically all present-day 12-oz. size carbonated beverage cans feature an easy-open can end.
In spite of the above-noted advantages of metal cans over bottles, threaded bottles have generally been preferred for carbonated beverage containers larger than 12 ounces because such beverages are usually consumed in quantities of less than 12 ounces at a time, and bottles having a threaded closure thereon have been better adapted for resealing to retain carbonation in the beverage than have metal cans.
A variety of suggestions for providing a seal or reseal of a metal can end have been made. Ruskin U.S. Pat. No. 3,664,541, for example, describes a resilient body that is adapted to plug a conventional opening in the can end; that is, an opening made by lifting and pulling a tab connected to a portion of the can end defined by a score line. The end metal tears along the score line and the tab and weakened portion are then discarded, and Ruskin's device is used thereafter to seal the opening.
Another suggestion for resealing a can end is provided in Balocca et al U.S. Pat. No. 3,804,287. Balocca et al describes a can end having a dispensing aperture which is initially sealed with an adhesive patch adhered to the inner side of the end around the aperture. A resilient resealing member comprised of a plug on one end and a pull handle on the other end is disposed on the outside of the can end with the plug adhesively bonded to the sealing patch. When the handle is pulled, the patch portion defined by the periphery of the aperture is torn away to gain access to the container contents. The opening can then be resealed by pressing the plug downward into the aperture. The reseal is effected by an interference fit between the aperture edge and an upper portion of the plug which is larger in cross section than the aperture.
It may be seen that in plug seals, such as those described in the aforementioned Ruskin and Balocca et al patents, an effective reseal is dependent upon the interaction between the plug and the single layer of metal in the can end defining the opening. In such a case, the force required to wedge the plug into the opening sufficiently to resist being blown out of the opening by the internal pressure within a carbonated beverage can must be at least as much as the blow-out force generated by gas dissociating from the beverage. Since the blow-out force in such a container can exceed 35 pounds, the plug may be difficult to insert, as well as remove when it is desired to gain access to the can contents.
A combination opener-reclosure device for a can end is described in Wells et al U.S. Pat. No. 3,880,319. The device is movably attached to the can end and a plug portion is adapted to partially sever a flap defined by a line of weakness, such as a score line, for example, in the can end. With the opener-plug properly positioned in relation to the line of weakness, downward pressure on the device causes rupture of the can end along the line of weakness and the flap is hinged inwardly into the can. The device is then removed from the opening to provide access to the can contents. If only a portion of the contents are consumed, and it is desired to reclose the end, the plug portion is again moved to position it above the opening, and the plug portion is forced into the opening by applying downward pressure.
The foregoing examples describe but a few of the many proposals that have been made to provide an easy-open can end which can be resealed or reclosed.